Summary
The effect of insulin on cyclic nucleotide phosphodiesterase (PDE) in rat luteal cells
was studied. Cells were obtained from PMSG/hCG primed rats and further incubated or
not with insulin. The hormone produced an increase of enzyme activity after a 10 min
incubation of intact cells. Maximal stimulation was achieved at 0.2 nM of insulin.
Two peaks of cyclic nucleotide phosphodiesterase activity were resolved after chromatography
of cell cytosolic extracts on DEAE-cellulose. These peaks (I and II) were active with
cAMP as substrate but only peak I was active with cGMP. The enzyme activity of both
peaks was increased in cells treated with insulin. Phosphodiesterase activity in the
two peaks show two kinetic components for cAMP hydrolysis, one of high affinity (Km
2-4 μM) and the other of low affinity (47-56 μM). Treatment of the cells with insulin
produced a 2 to 8 fold increase of the Vmax of these peaks.
In addition after stimulation with insulin, the activation of peak I phosphodiesterase
by calmodulin was less effective.
Key-Words
Luteal Cells
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Insulin Regulation
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Cyclic Nucleotide Phosphodiesterase
